Chapter 2 The nutrients in food
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I'm about to carry out an investigation on the Vitamin C content of food (an investigation based around the food special study practical). I've worked out how to do the practical work but can find very little theory to back up my predictions. Can you give me some ideas?
Ulex says ...
I am making the assumption that by 'theory' you mean: 'What happens to ascorbic acid when it decomposes?'
This turns out to be rather good question and one which I ought to have asked myself long ago. It also begs the question: 'Why is ascorbic acid a reducing agent - i.e. what is it oxidised to?'
I think the first step of oxidation of ascorbic acid is:
L-ascorbate + oxygen -> dehydroascorbate + water
a reaction which is catalysed by an enzyme called ascorbate oxidase. I think this reaction is what starts off the degradation of ascorbic acid in vegetables with age and may go some way towards explaining why acidic fruits lose their ascorbic acid content more slowly. It doesn't seem to explain why high temperatures reduce ascorbic acid concentration, however.
It does seem rather strange that detailed equations are lacking in most accounts.
Risk assessment
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updated: 02 June 2005
